diff --git a/dist/expand-envs.js b/dist/expand-envs.js
index ccb4853..59346d2 100644
--- a/dist/expand-envs.js
+++ b/dist/expand-envs.js
@@ -6,6 +6,6 @@ export function expandEnvs(str, envs) {
     return str.replace(/(?<!\\)\$[a-zA-Z0-9_]+/g, (varName) => {
         const varValue = envs[varName.slice(1)];
         // const test = 42;
-        return varValue === undefined ? varName : varValue.toString();
+        return varValue ?? varName;
     });
 }
diff --git a/dist/parse-env-file.js b/dist/parse-env-file.js
index 81f6c3e..2a2b9a0 100644
--- a/dist/parse-env-file.js
+++ b/dist/parse-env-file.js
@@ -49,7 +49,7 @@ export async function getEnvFileVars(envFilePath) {
  */
 export function parseEnvString(envFileString) {
     // First thing we do is stripe out all comments
-    envFileString = stripComments(envFileString.toString());
+    envFileString = stripComments(envFileString);
     // Next we stripe out all the empty lines
     envFileString = stripEmptyLines(envFileString);
     // Merge the file env vars with the current process env vars (the file vars overwrite process vars)
@@ -110,7 +110,7 @@ export function normalizeEnvObject(input, absolutePath) {
     const env = {};
     for (const [key, value] of Object.entries(input)) {
         // we're intentionally stringifying the value here, to
-        // match what `child_process.spawn` does when loading 
+        // match what `child_process.spawn` does when loading
         // env variables.
         // eslint-disable-next-line @typescript-eslint/restrict-template-expressions
         env[key] = `${value}`;
diff --git a/src/expand-envs.ts b/src/expand-envs.ts
index 47a56d5..60b66cf 100644
--- a/src/expand-envs.ts
+++ b/src/expand-envs.ts
@@ -8,6 +8,6 @@ export function expandEnvs(str: string, envs: Environment): string {
   return str.replace(/(?<!\\)\$[a-zA-Z0-9_]+/g, (varName) => {
     const varValue = envs[varName.slice(1)]
     // const test = 42;
-    return varValue === undefined ? varName : varValue.toString()
+    return varValue ?? varName
   })
 }
diff --git a/src/parse-env-file.ts b/src/parse-env-file.ts
index a646cf8..296c6ac 100644
--- a/src/parse-env-file.ts
+++ b/src/parse-env-file.ts
@@ -56,7 +56,7 @@ export async function getEnvFileVars(envFilePath: string): Promise<Environment>
  */
 export function parseEnvString(envFileString: string): Environment {
   // First thing we do is stripe out all comments
-  envFileString = stripComments(envFileString.toString())
+  envFileString = stripComments(envFileString)
 
   // Next we stripe out all the empty lines
   envFileString = stripEmptyLines(envFileString)
@@ -126,7 +126,7 @@ export function normalizeEnvObject(input: unknown, absolutePath: string): Enviro
   const env: Environment = {};
   for (const [key, value] of Object.entries(input)) {
     // we're intentionally stringifying the value here, to
-    // match what `child_process.spawn` does when loading 
+    // match what `child_process.spawn` does when loading
     // env variables.
     // eslint-disable-next-line @typescript-eslint/restrict-template-expressions
     env[key] = `${value}`